Problem solved... it was unknowingly self inflicted.
I use Assisted Install and had set NONEWDATABASES=1, thinking this was only related to File>New Solution... it didn’t occur to me that this extended to Export records, which, of course, it does, since export creates a new fmp12 file.
I’ve adjust the assisted install parameters and reinstalled… all is well.
Thanks for your help. Maybe my error will help someone else who has made the same assumption.

Just some further clarification per Lee's suggestion:
I upgraded to FMS 16. This was smooth fast and simple, though I am struggling a bit with installing a wildcard SSL Cert, but that' another story for another day.
Most of my network is running PCs and all of those are Win 7. I have a handful of Mac clients but they all work fine with this exporting issue... it's only the Win 7 machines having this issue.
My personal workstation used for development and such is a late generation Macbook Pro running Sierra and Parallels Desktop for Windows development/testing.
Thank you all for you help.

Yes, I tried using no extension and letting FM add it and I tried adding the .fmp12 extension. I didn't bother to record all that. I've also checked disk and user permissions. I am convinced it is something in the new v16 because, as the video shows, v15 works just fine. FM Tech hasn't been much help.

Hi,
Has anyone else found that you are unable to export .fmp12 records from FM 16? I use this step in many scripts and the first machine I upgraded ( out of 48 ) I get the "unable to save file" error every time. FM 15 works, FM 16 fails on the same DB, same table, same record set. I can't even export manually.
I made a screen movie here: https://www.youtube.com/watch?v=iOGcm4bt86o